Landslide is a global environmental geological hazard caused by natural or human activities. Since the impoundment of the Three Gorges reservoir area, the geological disasters such as collapses, ...landslides and other kinds of geological disasters increased obviously due to the periodic fluctuation of the water level in the Yangtze River. Wanzhou District is located in the center of the Three Gorges Reservoir Area, which plays an important role in the prevention and control of geological hazards in the whole Three Gorges Reservoir Area. This is because a large number of deep bedrocks old landslides are distributed among this region, such as Taibaiyan ancient landslide, Caojiezi ancient landslide, Anlesi ancient landslide, Pipaping ancient landslide, and Diaoyanping ancient landslide. In this study, Quasi-Persistent Scatterers InSAR (QPS-InSAR) time-series method is proposed to identify and monitor the ancient landslides in Wanzhou. In this method, the High-coherent test is applied to Quasi-Persistent Scatterers (PSC) selection, and PSC and persistent scatterer are combined to improve the density of measurement points in vegetation area. The QPS-InSAR method is also characterized by the appropriate combination of differential interferograms produced by a Minimum Spanning Tree and the employment of the phase triangulation algorithm to estimate the optimal phase. This technique was performed on 8 scenes of L-band ALOS PALSAR ascending data acquired during 2015–2018, then deformation rate maps and time series for ancient landslide were generated, which were applied to retrieve time series displacement for the large-scale landslide in Wanzhou District. The experiment results show that there are obvious landslide deformation patterns detected in this region with displacement velocity larger than − 21 mm/yr during the observation period. Finally, the influencing factors such as geological conditions, distribution of rainfall and reservoir water level change in the Three Gorges Reservoir area, and deformation mechanism of Wanzhou landslide are analyzed. The monitoring results will help the local government to carry out regular landslide inspection and strengthen landslide disaster early warning.
Flexible all‐solid‐state asymmetric supercapacitors (ASCs) are fabricated from a novel anode – WO3–x/MoO3–x core/shell nanowires on carbon fabric – and a polyaniline cathode (figure). In addition to ...the high electrochemical performance of the devices, other characteristics, such as low toxicity, flexibility, environmental compatibility, light weight, and low requirements for packaging, make the all‐solid‐state ASCs potential candidates for applications in energy storage, flexible electronics, and other consumer electronics.
Over the past few years, the rapid development of tactile sensing technology has contributed significantly to the realization of intuitional touch control and intelligent human-machine interaction. ...Apart from physical touch or pressure sensing, proximity sensing as a complementary function can extend the detection mode of common single functional tactile sensors. In this work, we present a transparent, matrix-structure dual functional capacitive sensor which integrates the capability of proximity and pressure sensing in one device, and the excellent spatial resolution offered by the isolated response of capacitive pixels enables us to realize precise location identification of approaching objects and loaded pressure with fast response, high stability and high reversibility.
The monitoring data of landslide deformation are characterized by non-smooth, nonlinear and random changes, and the cumulative changes of the monitored objects have both monotonous growth trends and ...short-term fluctuations. The GM(1,1) model can get better results only when the data series are monotonous. Due to the limitations of the model, the prediction accuracy of the GM(1,1) model is limited to a certain extent. An improved algorithm based on the GM(1,1) model and the empirical mode decomposition (EMD-GM(1,1) model) for deformation prediction was presented to improve the forecast accuracy in this paper. Firstly, EMD was used to effectively separate the nonlinear high-frequency and low-frequency components hidden in the deformation sequence; then the moving average method was applied to build a prediction model for high-frequency component, and the GM(1,1) was applied to build the prediction model for low-frequency one according to the characteristics of each component; finally, the predicted value of each component was superimposed. The experimental results indicate that the optimized EMD-GM(1,1) model combines the advantages of the two models to separate effectively the different frequency components of the deformation sequence, which has higher prediction accuracy. Compared with the conventional GM(1,1) model, DGM(2,1) model and the Linear fitting model, the proposed model could satisfactorily describe the landslide deformation prediction practically.
Tribotronics has attracted great attention owing to the demonstrated triboelectrification-controlled electronics and established direct modulation mechanism by external mechanical stimuli. Here, a ...nanoscale triboelectrification-gated transistor has been studied with contact-mode atomic force microscopy and scanning Kevin probe microscopy. The detailed working principle was analyzed at first, in which the nanoscale triboelectrification can tune the carrier transport in the transistor. Then with the manipulated nanoscale triboelectrification, the effects of contact force, scan speed, contact cycles, contact region and charge diffusion on the transistor were investigated, respectively. Moreover, the manipulated nanoscale triboelectrification serving as a rewritable floating gate has demonstrated different modulation effects by an applied tip voltage. This work has realized the nanoscale triboelectric modulation on electronics, which could provide a deep understanding for the theoretical mechanism of tribotronics and may have great applications in nanoscale transistor, micro/nano-electronic circuit and nano-electromechanical system.
Thermal pre-oxidation of polyacrylonitrile (PAN) fibers is a time-consuming and energy-consuming step in the production of PAN-based carbon fibers. In this paper, the effect of temperature on the ...structures and properties of PAN fibers cyclized in the supercritical carbon dioxide (Sc-CO₂) medium was studied. The thermal behaviors of the PAN fibers were investigated by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The cyclization reaction was sensitive to the heating temperature and gas atmosphere. The FT-IR results of the PAN fibers treated in the Sc-CO₂ confirmed that the degree of cyclization increased with the increase of the cyclization temperature. Compared with the PAN fibers treated in the air, the PAN fibers treated in the Sc-CO₂ showed a higher degree of cyclization even at the same temperature. These findings might be related to the osmotic action of Sc-CO₂ causing the fibers to be further arranged in a regular manner, which was favorable for the cyclization reaction. Moreover, as one kind of high diffusion and high heat transfer media, the heat release during the cyclization of PAN fibers could be quickly removed by Sc-CO₂, which achieved the progress of the rapid-entry cyclization reaction.
Fault activity property is one of the main reasons caused by the motion of crustal fault, and the research of fault activity characteristics has become an important direction in the study of ...earthquake prediction, which is an important source of new theory and new method in earthquake prediction science. The disastrous May 12, 2008, Mw7.9 Wenchuan earthquake in the Longmenshan fault zone (LFZ) took the local population as well as scientists by surprise. To analyze the temporal and spatial deformation characteristics of the Mao county–Wenchuan fault, the Beichuan-Yingxiu fault, and Jiangyou-Guan County in the central south segment of the LFZ after the Wenchuan earthquake, the SBAS-InSAR method was adopted to derive surface deformation rate with 20 Envisat SAR images acquired between August 6, 2007, and July 26, 2010. Our analysis shows that the overall movement speed of LFZ increased significantly, reaching about − 40 mm/year, which shows a dextral compression strike-slip. From west to east, the velocity changes of each section are different, and the movement of the front-range fault is dominant in the middle and south sections of Longmenshan, which is close to the epicenter. The reason may be related to the fact that the middle and south section of Longmenshan is the epicenter of the earthquake. The southern and mid-southern sections of the LFZ change from west to east, and the direction of profile movement increases gradually. In the middle and north segment of the fault zone between the two, the variation characteristics are not obvious. To a certain extent, it indicates that the fault is characterized by dextral strike-slip compression in the southern segment and the mid-southern segment. The difference in the profile movement direction in the LFZ may be related to the stress release of the southern segment of the LFZ after the earthquake while the movement of the northern segment of the LFZ was blocked. The research results will reveal the mechanism of earthquake pregnancy and earthquake generation of LFZ, enrich the knowledge of the impact on the aftershock distribution of the Wenchuan earthquake, and promote the development of earthquake prediction research.
Triboelectric nanogenerators (TENGs) have demonstrated enormous potential applications for acquiring human motion energy and ambient mechanical energy, which is the foundation of energy for the new ...era. However, with alternating current (AC) pulse and huge inherent impedance, the TENGs usually exhibit low‐energy supply efficiency when either powering conventional electronics or charging energy storage devices directly. Efficient power management has always been a technical bottleneck for the TENGs toward practical applications in self‐powered microsystems. Over the past years, several strategies of power management have been proposed, such as rectification, electromagnetic transformation, capacitive transformation, and direct current (DC) conversion, which can be used for voltage regulation, impedance matching, and efficiency improvement for electronics. Herein, the recent advances on power management for TENGs are systematically reviewed and analyzed, which has exhibited manageable triboelectric power by electronics as an important research issue of TENGs. Finally, the existing challenges and future perspectives in this field are discussed.
An overview of power management for triboelectric nanogenerators (TENGs) is presented, including two main sections. The first is a systematic summary and comparison of the recent advances on power management for TENGs. The second is an outlook of TENGs with the power management module to power various advanced intelligent systems.
Abstract
Electrically modulated varifocal liquid lenses, which are usually modulated by an external high voltage power source, have attracted much attention due to their bright application prospects ...in artificial optical systems. Here, a triboelectric nanogenerator (TENG)-based varifocal liquid lens (TVLL) has been demonstrated, in which the focal length can be directly modulated by external mechanical sliding. A dielectrophoretic force is generated by the TENG through the transfer of triboelectric charges in the asymmetric electrodes, which is used to continuously change the shape of the air–liquid interface between concave and convex without any complicated boost converter. Moreover, a triboelectric magnifying glass based on the accurate modulation effect of the TVLL on a light beam has been demonstrated. In this work, the TENG is used as a medium to modulate and accurately control the focal length of the liquid lens by an external mechanical stimulus, which may have great applications in micro-optical-electro-mechanical systems (MOEMS), human–machine interaction, artificial vision systems, etc.
Dam deformation monitoring data are generally characterized by non-smooth and no-saturated S-type fluctuation. The grey Verhulst model can get better results only when the data series is ...non-monotonic swing development and the saturated S-shaped sequence. Due to the limitations of the grey Verhulst model, the prediction accuracy will be limited to a certain extent. Aiming at the shortages in the prediction based on the traditional Verhulst model, the optimized grey Verhulst model is proposed to improve the prediction accuracy of the dam deformation monitoring. Compared with those of the traditional GM (1,1) model, the DGM (2,1) model, and the traditional Verhulst (1,1) model, the experimental results show that the new proposed optimized Verhulst model has higher prediction accuracy than the traditional gray model. This study offers an effective model for dealing with the non-saturated fluctuation sequence to predict dam deformation under uncertain conditions.
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